Faculty Profiles - TOYODA, Hirotaka

Papers - TOYODA, Hirotaka

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*Fine Structure of O Kinetic Energy Distribution in RF Plasma and Its Formation Mechanism Reviewed

H.Toyoda, K. Goto, T. Ishijima, T. Morita, N. Ohshima, K. Kinoshita

Applied Physics Express Vol. 2 ( 12 ) page： 126001-(1-3) 2009.11

Design of Large-Area Surface Wave Plasma Excited by Slotted Waveguide Antennas with Novel Power Divider Reviewed

Tatsuo Ishijima, Hirotaka Toyoda, Yudai Takanishi, and Hideo Sugai

Jpn. J. Appl. Phys. Vol. 50 page： 036002 2011.3

*Generation processes of super-high-energy atoms and ions in magnetron sputtering plasma Reviewed

Y. Takagi, Y. Sakashita, H. Toyoda, and H. Sugai

Vacuum Vol. 80 ( 6 ) page： 581-587 2006.3

*Evidence of Radical-free Etching of SiO₂ by Fluorocarbon Molecules under Ion Bombardment Reviewed

N. Takada, H. Toyoda and H. Sugai

Transacitons of the Materials Research Society of Japan Vol. 30 ( 1 ) page： 319-322 2005

*Suppression of Oxygen Impurity Incorporation into Silicon Films Prepared from Surface-Wave Excited H₂/SiH₄ Plasma Reviewed

S. Somiya, H. Toyoda, Y. Hotta and H. Sugai

Jpn. J. Appl. Phys. Vol. 43 ( 11A ) page： 7696-7700 2004

Measurement of energy-resolved ion angular distribution in a dual-frequency capacitively coupled argon plasma Reviewed

Kim, Dohan; Kawamura, Shunya; Naito, Masayoshi; Iino, Daiki; Fukumizu, Hiroyuki; KURIHARA, Kazuaki; Suzuki, Haruka; TOYODA, Hirotaka

Japanese Journal of Applied Physics Vol. 64 page： 05SP15-1 - 05SP15-7 2025.5

Angular distribution measurement of high-energy ions and neutrals impinging on an RF electrode in a dual-frequency capacitively-coupled Ar plasma Invited Reviewed

Shunya Kawamura, Dohan Kim, Keita Ichikawa, Haruka Suzuki, Daiki Iino, Hiroyuki Fukumizu, Kazuaki Kurihara and Hirotaka Toyoda

Plasma Sources Science and Technology 2025.5

Dry Process 2023 Open Access

Koga K., Takeda K., Toyoda H., Ishikawa K., Ichiki T., Nunomura S., Kurihara K., Kuboi N., Ohta T., Takenaka K.

Japanese Journal of Applied Physics, Part 1: Regular Papers and Short Notes and Review Papers Vol. 63 ( 8 ) 2024.8

Influence of bias voltage on the Ar/CH2F2/O2 plasma etching of Si3N4 films Reviewed

Kuboi, S; Kataoka, J; Iino, D; Kurihara, K; Toyoda, H; Fukumizu, H

JAPANESE JOURNAL OF APPLIED PHYSICS Vol. 63 ( 8 ) 2024.8

Language：English Publishing type：Research paper (scientific journal) Publisher：Japanese Journal of Applied Physics, Part 1: Regular Papers and Short Notes and Review Papers

The etching mechanism of silicon nitride (Si3N4) films depending on peak-to-peak bias voltage ( V pp ) in an Ar/CH2F2/O2 gas-mixture plasmas for high-aspect-ratio etching process was investigated. It was observed that the Si3N4 film etch rate initially decreased with an increase in the V pp up to 3630 V, but then increased beyond this threshold. This unusual etching behavior can be attributed to the formation of a modified layer on the surface of the Si3N4 film. The characteristics of the modified layer, such as thickness and atomic composition, were found to be strongly influenced by the ion energy and gas chemistry of the process conditions.

DOI： 10.35848/1347-4065/ad6d20

Web of Science

Scopus

Evaluation of the spatial structure of multiline emission in a capacitively coupled plasma using tomographic reconstruction Reviewed

Kyuzo, M; Harada, K; Izumi, R; Suzuki, H; Toyoda, H

JAPANESE JOURNAL OF APPLIED PHYSICS Vol. 63 ( 5 ) 2024.5

Authorship：Last author Language：English Publishing type：Research paper (scientific journal) Publisher：Japanese Journal of Applied Physics

By imaging a capacitively coupled plasma from multiple directions using telecentric lens cameras and optical bandpass filters, the spatial structure of emission at specific wavelengths was reconstructed using the Tikhonov-Phillips regularization method. Camera parameters, crucial for relating three-dimensional structures to two-dimensional images, were evaluated experimentally to avoid a complex analytical approach. Assuming an axisymmetric emission profile, 750.4 nm Ar and 585.2 nm Ne emissions from Ar/Ne mixture plasma were reconstructed. The pressure dependence of the reconstructed Ar profile showed a similar trend to that of the two-dimensional emission images. The spatial structure of the emission intensity ratio of Ne to Ar from the reconstructed Ar and Ne profiles agreed well with a spatial distribution of electron temperatures measured with a Langmuir probe.

DOI： 10.35848/1347-4065/ad46b0

Web of Science

Scopus

Time-varying mechanism of ion composition in a pulse-modulated Ar/C4F8/O2 dual-frequency capacitively coupled plasma Reviewed

Kuboi, S; Kato, H; Akatsuka, Y; Suzuki, H; Toyoda, H

JAPANESE JOURNAL OF APPLIED PHYSICS Vol. 63 ( 1 ) page： 016001 2024.1

Language：English Publishing type：Research paper (scientific journal) Publisher：Japanese Journal of Applied Physics

The time-varying mechanism of the positive-ion composition in a pulse-modulated Ar/C4F8/O2 dual-frequency capacitively coupled plasma was investigated in detail using a quadrupole mass spectrometer equipped with an electrostatic energy analyzer. Time-resolved measurements of the ion composition with respect to the pulse-off period ( T off ) revealed that the electron temperature ( T e ) just after turning on the pulse is an important factor in determining the ratio of the ionization rates of the Ar+ and Cx Fy + ions. The time-varying phenomenon of the ion composition was also investigated through a numerical analysis based on the particle balance model, considering the production and loss rates of ions, ion-ion recombination processes, and ion-molecule reactions. When the VHF power ( P VHF ) was increased, a decrease in the ambipolar diffusion loss time constants of the ions ( τ loss i ) was observed, and the change in electronegativity was pointed out as the cause of this phenomenon.

DOI： 10.35848/1347-4065/ad121f

Web of Science

Scopus

Mass spectroscopic measurement of time-varying ion composition in a pulse-modulated Ar/C4F8/O2 dual-frequency capacitively coupled plasma International journal

Shuichi Kuboi, Haruhito Kato, Yuto Seki, Haruka Suzuki and Hirotaka Toyoda

Japanese Journal of Applied Physics Vol. 62 ( SI ) page： SI1003 2023.7

Polyvinyl alcohol-potassium iodide gel probe to monitor the distribution of reactive species generation around atmospheric-pressure plasma jet

Tran, TN; Hu, M; Ogasawara, T; Iwata, Y; Suzuki, H; Sakamoto, J; Akiyoshi, M; Toyoda, H; Matsuura, H

PLASMA SCIENCE & TECHNOLOGY Vol. 25 ( 3 ) 2023.3

Language：English Publishing type：Research paper (scientific journal) Publisher：Plasma Science and Technology

This study proposes polyvinyl alcohol-potassium iodide (PVA-KI) as a novel gel chemical probe. The probe uses the reactions among PVA, KI, water, borax, and oxidative species to visualize the distribution of reactive species. This method provides information regarding the distribution of reactive species by coloration on the gel surface. The effects of the surrounding gas phase on the distribution and diffusion of the reactive species are also investigated using the PVA-KI gel probe. Further, the relationship between the irradiation distance and reactive species diffusion is determined on the surface of the PVA-KI probe with and without plastic shielding. Adjusting the irradiation distance appropriately leads to an increase in the modified area as detected by the PVA-KI gel probe analysis. The relative concentration distributions of the reactive species are also obtained from visualized color distributions measured using a colorimeter. Furthermore, reactive species generation by long-scale line plasma is confirmed by the color reaction on the PVA-KI gel surface, with a greater area being covered by an atmospheric-pressure pulsed microwave line plasma source.

DOI： 10.1088/2058-6272/ac9891

Web of Science

Scopus

Influence of small ground surface on plasma property in an inductively-coupled plasma with floating liner International journal

Manabu Kyuzo, Yukinori Chiba, Haruka Suzuki and Hirotaka Toyoda

Japanese Journal of Applied Physics Vol. 62 ( SA ) page： SA1008-1 - SA1008-7 2023.1

Language：English Publishing type：Research paper (scientific journal) Publisher：Japanese Journal of Applied Physics

Currently, the components of semiconductor processing chamber are coated with oxides to avoid metal contamination. As a result, electrical ground is hidden from the plasma. In this study, we experimentally investigate the effect of small ground surfaces in an inductively-coupled plasma (ICP) generated in an electrically floating liner. Peak-to-peak and DC voltages at a biasing stage and a floating liner are measured as a function of stage peak-to-peak voltage for various ICP powers and the ground surface areas. The results show that the stage and liner voltages vary with changing ground surface area due to a change in sheath thickness. The analytical plasma potentials, calculated from the experimental values are compared with the simulation results, show good agreement. It is suggested that under low biased voltage and high ICP power conditions, such as in the atomic layer etching process, the small ground surface affects the potential structure in the chamber.

DOI： 10.35848/1347-4065/ac7e19

Web of Science

Scopus

Other Link： https://iopscience.iop.org/article/10.35848/1347-4065/ac7e19

Experimental study on boron distribution and transport at plasma-facing components during impurity powder dropping in the Large Helical Device Reviewed Open Access

Kawate T., Ashikawa N., Goto M., Oishi T., Kawamoto Y., Toyoda H., Shoji M., Kawamura G., Masuzaki S., Nespoli F., Gilson E. P., Lunsford R., Suzuki C., Nagy A., Gates D.

NUCLEAR FUSION Vol. 62 ( 12 ) page： 126052-1 - 126052-9 2022.12

Bubbling phenomenon of liquidized Sn-Bi-Li-Er alloy under hydrogen plasma exposure Reviewed

Tamura Kota, Miyazawa Junichi, Masuzaki Suguru, Tokitani Masayuki, Hamaji Yukinori, Toyoda Hirotaka

JAPANESE JOURNAL OF APPLIED PHYSICS Vol. 61 ( 10 ) page： 106005 2022.10

Dry Process

Japanese Journal of Applied Physics Vol. 61 ( SI ) 2022.7

High-speed hydrophilic and ashing treatments of polyimide using Ar/O-2 atmospheric-pressure microwave line plasma Reviewed

Japanese Journal of Applied Physics Vol. 61 ( SI ) page： 1008-1 - 1008-5 2022.7

Enhancement of the ion flux to the substrate through high-voltage biasing in an electron cyclotron resonance plasma and its application to high-speed deposition of conductive carbon film Reviewed

Bae Hansin, Hamaguchi Ikumi, Sasai Kensuke, Suzuki Haruka, Toyoda Hirotaka

JAPANESE JOURNAL OF APPLIED PHYSICS Vol. 60 ( 12 ) 2021.12

Authorship：Last author,　Corresponding author Language：English Publishing type：Research paper (scientific journal) Publisher：Japanese Journal of Applied Physics

A method for enhancing ion flux to the substrate via high-voltage pulse biasing is investigated in an electron cyclotron resonance plasma. When high-voltage pulse biases above 500 V are applied to the stage, an increase in the stage current is observed, especially in the case of diverging magnetic field configurations in front of the bias stage. The growth and decay time constants of the plasma density and emission intensity are evaluated using a time-resolved Langmuir probe and emission spectroscopy while the pulse is on, and the enhancement of the ionization rate during the bias application is estimated using the zero-dimensional global model. The estimated density enhancement from the model is in good agreement with the measured one. From the numerical simulation of secondary electron trajectory, it is concluded that the electron confinement from the magnetic field is the key factor in plasma density enhancement during stage biasing. Using the high-density plasma produced by the bias voltage, conductive carbon is deposited at a high deposition rate of ∼4 nm s-1.

DOI： 10.35848/1347-4065/ac32b6

Web of Science

Scopus

Angular distribution measurement of high-energy argon neutral and ion in a 13.56 MHz capacitively-coupled plasma Reviewed

Keita Ichikawa, Manh Hung CHU, Makoto Moriyama, Naoya Nakahara, Haruka Suzuki, Daiki Iino, Hiroyuki Fukumizu, Kazuaki KURIHARA and Hirotaka TOYODA

Applied Physics Express Vol. 14 ( 126001 ) page： 126001-1 - 126001-5 2021.11

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Papers - TOYODA, Hirotaka